Generally, according to an engine (an internal combustion engine) for a vehicle and the like having a lock mechanism, a phase formed between a driving-side rotating member and a driven-side rotating member is set at an appropriate initial phase, so that the engine is started while forming the initial phase. Accordingly, an intake timing and an ignition timing of the engine are optimized.
Disclosed in JPH11-173119A is a valve timing control apparatus, which is provided at an internal combustion engine having a lock mechanism. According to the valve timing control apparatus disclosed in JPH11-173119A, a phase formed between a driving-side rotating member and a driven-side rotating member when the internal combustion engine is stopped is returned to a phase formed when the internal combustion engine is started by using an inertial rotation of the engine, which is generated when the internal combustion engine is stopped.
More specifically, according to the valve timing control apparatus disclosed in JPH11-173119A, in a case where the internal combustion engine is stopped, both of a retarded angle chamber and an advanced angle chamber, each of which is defined by the driving-side rotating member and the driven-side rotating member, are connected to passages that are used for supplying and discharging the operation oil therefrom. Accordingly, while the internal combustion engine is being rotated by its inertia after the internal combustion engine is stopped, the operation oil is discharged from the retarded angle chamber and the advanced angle chamber via the respective passages. As a result, the driven-side rotating member rotates relative to the driving-side rotating member towards the advanced angle chamber (i.e. towards a retarded angle phase, in a retarded angle direction) by a reaction force acting on a camshaft in order to actuate the lock mechanism.
In other words, the valve timing control apparatus disclosed in JPH11-173119A is configured so that the driven-side rotating member inertially rotates when the internal combustion engine is stopped and so that the driven-side rotating member smoothly moves towards the advanced angle chamber (i.e. towards the retarded angle phase, in the retarded angle direction) by using the reaction force acting on the camshaft. The driving-side rotating member and the driven-side rotating member rotate so as to form the advanced angle phase (i.e. in the advanced angle direction) by inertia, while a rotation of the driven-side rotating member is intermittently interrupted by the reaction force acting on the camshaft. Accordingly, a vane provided at the driven-side rotating member moves towards the advanced angle chamber (i.e. towards the retarded angle phase) while repeatedly moving towards and away from the advanced angle chamber (i.e. in the retarded angle direction). In other words, the vane moves towards the advanced angle chamber (i.e. in the retarded angle direction) in response to an average torque of a torque fluctuation of the cam. In this case, because both of the advanced angle chamber and the retarded angle chamber are in communication with an outside of the valve timing control apparatus, the operation fluid freely flows towards/from the advanced angle chamber and the retarded angle chamber, which are formed across the vane. In other words, according to the valve timing control apparatus disclosed in JPH11-173119A, the vane (i.e. the driven-side rotating member) is smoothly moved, so that the phase formed between the driving-side rotating member and the driven-side rotating member is changed to a lock phase in order to smoothly start the engine.
However, in the valve timing control apparatus disclosed in JPH11-173119A, the operation fluid may not be appropriately discharged from the advanced angle chamber and the retarded angle chamber only by connecting the advanced angle chamber and the retarded angle chamber with the respective flow passages for supplying and discharging the operation fluid when the internal combustion engine is stopped. For example, even in a case where the operation fluid freely flow into/from the advanced angle chamber and the retarded angle chamber (i.e. even in a case where a flow of the operation fluid is not controlled by a valve and the like), the operation fluid remains within the advanced angle chamber and the retarded angle chamber while the internal combustion engine is being completely stopped. Therefore, for example, in a case where the internal combustion engine stalls while an ambient temperature is low and while a temperature of the operation fluid is not sufficiently increased, an operation resistance of the vane may increase because viscosity of the operation fluid remaining within the advanced angle chamber and the retarded angle chamber is high. Accordingly, the lock mechanism may not actuate before the inertial rotation of the driven-side rotating member is completely stopped.
Furthermore, according to the valve timing control apparatus disclosed in JPH11-173119A, even in a case where the driving-side rotating member and the driven-side rotating member form an initial phase, by which the valve timing control apparatus is locked, the lock mechanism may be improperly actuated. In other words, even if the driving-side rotating member and the driven-side rotating member form the initial phase, both of the driving-side rotating member and the driven-side rotating member still rotate relative to each other when the internal combustion engine is stopped. Therefore, a time for the driving-side rotating member and the driven-side rotating member forming the initial phase is relatively short. In this case, the operation fluid remains within an engagement groove of the lock mechanism. Accordingly, an engagement piece may not be inserted into the engagement groove because the fluid remaining therewithin causes resistance. The above-described situation is more likely to occur when the ambient temperature is low, where the viscosity of the operation oil becomes high.
Accordingly, there is room for the known valve timing control apparatus to be improved so that the valve timing control apparatus smoothly starts the internal combustion engine under various circumstances and environments.
A need thus exists to provide a valve timing control apparatus which is not susceptible to the drawback mentioned above.